Posting a File and Associated Data to a RESTful WebService preferably as JSON

Question

This is probably going to be a stupid question but I m having one of those nights  In an application I am developing RESTful API and we want the client to send data as JSON  Part of this application requires the client to upload a file  usually an image  as well as information about the image   I m having a hard time tracking down how this happens in a single request   Is it possible to Base64 the file data into a JSON string   Am I going to need to perform 2 posts to the server   Should I not be using JSON for this   As a side note  we re using Grails on the backend and these services are accessed by native mobile clients  iPhone  Android  etc   if any of that makes a difference

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Here is my approach API  i use example  - as you can see  you I don t use any file id  uploaded file identifier to the server  in API   Create photo object on server   POST   projects  project id  photos     body    name   quot some schema jpg quot   comment   quot blah quot    response  photo id   Upload file  note that file is in singular form because it is only one per photo    POST   projects  project id  photos  photo id  file  body  file to upload  response  -    And then for instance   Read photos list  GET   projects  project id  photos  response    photo  photo  photo         array of objects    Read some photo details  GET   projects  project id  photos  photo id   response    id  666  name   some schema jpg   comment  blah    photo object    Read photo file  GET   projects  project id  photos  photo id  file  response  file content    So the conclusion is that  first you create an object  photo  by POST  and then you send second request with the file  again POST   To not have problems with CACHE in this approach we assume that we can only delete old photos and add new - no update binary photo files  because new binary file is in fact    NEW photo   However if you need to be able to update binary files and cache them  then in point 4 return also fileId and change 5 to  GET   projects  project id  photos  photo id  files  fileId

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I know that this thread is quite old  however  I am missing here one option   If you have metadata  in any format  that you want to send along with the data to upload  you can make a single multipart related request      The Multipart Related media type is intended for compound objects consisting of several inter-related body parts    You can check RFC 2387 specification for more in-depth details   Basically each part of such a request can have content with different type and all parts are somehow related  e g  an image and it metadata   The parts are identified by a boundary string  and the final boundary string is followed by two hyphens   Example   POST  upload HTTP 1 1 Host  www hostname com Content-Type  multipart related  boundary xyz Content-Length   actual-content-length   --xyz Content-Type  application json  charset UTF-8         name    Sample image        desc                     --xyz Content-Type  image jpeg   image data   image data   image data      --foo bar baz--

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RequestMapping value     uploadImageJson   method   RequestMethod POST      public  ResponseBody Object jsongStrImage  RequestParam value  image   MultipartFile image   RequestParam String jsonStr    -- use  com fasterxml jackson databind ObjectMapper convert Json String to Object

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Please ensure that you have following import  Ofcourse other standard imports  import org springframework core io FileSystemResource       void uploadzipFiles String token             RestBuilder rest   new RestBuilder connectTimeout 10000  readTimeout 20000           def zipFile   new File  testdata zip           def Id    001G00000          MultiValueMap lt String  String gt  form   new LinkedMultiValueMap lt String  String gt            form add  id   id          form add  file  new FileSystemResource zipFile           def urld     http   URL             def resp   rest post urld                header  X-Auth-Token   clientSecret              contentType  multipart form-data              body form                    println  resp    resp         println  resp    resp text         println  resp    resp headers         println  resp    resp body         println  resp    resp status

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I know this question is old  but in the last days I had searched whole web to solution this same question  I have grails REST webservices and iPhone Client that send pictures  title and description   I don t know if my approach is the best  but is so easy and simple   I take a picture using the UIImagePickerController and send to server the NSData using the header tags of request to send the picture s data   NSMutableURLRequest  request     NSMutableURLRequest alloc  initWithURL  NSURL URLWithString   myServerAddress      request setHTTPMethod   POST     request setHTTPBody UIImageJPEGRepresentation picture  0 5     request setValue   image jpeg  forHTTPHeaderField   Content-Type     request setValue   myPhotoTitle  forHTTPHeaderField   Photo-Title     request setValue   myPhotoDescription  forHTTPHeaderField   Photo-Description     NSURLResponse  response   NSError  error    NSURLConnection sendSynchronousRequest request returningResponse  amp response error  amp error     At the server side  I receive the photo using the code   InputStream is   request inputStream  def receivedPhotoFile    IOUtils toByteArray is    def photo   new Photo   photo photoFile   receivedPhotoFile   photoFile is a transient attribute photo title   request getHeader  Photo-Title   photo description   request getHeader  Photo-Description   photo imageURL    temp       if  photo save               File saveLocation   grailsAttributes getApplicationContext   getResource File separator    images   getFile       saveLocation mkdirs        File tempFile   File createTempFile  photo     jpg   saveLocation       photo imageURL   saveLocation getName           tempFile getName        tempFile append photo photoFile      else        println  Error        I don t know if I have problems in future  but now is working fine in production environment

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I asked a similar question here   How do I upload a file with metadata using a REST web service   You basically have three choices    Base64 encode the file  at the expense of increasing the data size by around 33   and add processing overhead in both the server and the client for encoding decoding  Send the file first in a multipart form-data POST  and return an ID to the client  The client then sends the metadata with the ID  and the server re-associates the file and the metadata  Send the metadata first  and return an ID to the client  The client then sends the file with the ID  and the server re-associates the file and the metadata

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You could try using https   square github io okhttp  library  You can set the request body to multipart and then add the file and json objects separately like so   MultipartBody requestBody   new MultipartBody Builder                    setType MultipartBody FORM                   addFormDataPart  uploadFile   uploadFile getName    okhttp3 RequestBody create uploadFile  MediaType parse  image png                      addFormDataPart  file metadata   json                   build             Request request   new Request Builder                    url  https   uploadurl com uploadFile                    post requestBody                   build             try  Response response   client newCall request  execute                  if   response isSuccessful    throw new IOException  Unexpected code     response                logger info response body   string

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You can send the file and data over in one request using the multipart form-data  content type   In many applications  it is possible for a user to be presented with a form  The user will fill out the form  including information that is typed  generated by user input  or included from files that the user has selected  When the form is filled out  the data from the form is sent from the user to the receiving application  The definition of MultiPart Form-Data is derived from one of those applications     From http   www faqs org rfcs rfc2388 html    quot multipart form-data quot  contains a series of parts  Each part is expected to contain a content-disposition header  RFC 2183  where the disposition type is  quot form-data quot   and where the disposition contains an  additional  parameter of  quot name quot   where the value of that parameter is the original field name in the form  For example  a part might contain a header  Content-Disposition  form-data  name  quot user quot  with the value corresponding to the entry of the  quot user quot  field   You can include file information or field information within each section between boundaries   I ve successfully implemented a RESTful service that required the user to submit both data and a form  and multipart form-data worked perfectly  The service was built using Java Spring  and the client was using C   so unfortunately I don t have any Grails examples to give you concerning how to set up the service  You don t need to use JSON in this case since each  quot form-data quot  section provides you a place to specify the name of the parameter and its value  The good thing about using multipart form-data is that you re using HTTP-defined headers  so you re sticking with the REST philosophy of using existing HTTP tools to create your service

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FormData Objects  Upload Files Using Ajax  XMLHttpRequest Level 2 adds support for the new FormData interface   FormData objects provide a way to easily construct a set of key value pairs representing form fields and their values  which can then be easily sent using the XMLHttpRequest send   method   function AjaxFileUpload         var file   document getElementById  files          var file   fileInput      var fd   new FormData        fd append  imageFileData   file       var xhr   new XMLHttpRequest        xhr open  POST     ws fileUpload do        xhr onreadystatechange   function              if  xhr readyState    4                 alert  success                      else if  uploadResult     success                alert  error               xhr send fd       https   developer mozilla org en-US docs Web API FormData

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I wanted send some strings to backend server  I didnt use json with multipart  I have used request params    RequestMapping value     upload   method   RequestMethod POST  public void uploadFile HttpServletRequest request          HttpServletResponse response   RequestParam  uuid   String uuid           RequestParam  type   DocType type           RequestParam  file   MultipartFile uploadfile    Url would look like   http   localhost 8080 file upload uuid 46f073d0 amp type PASSPORT   I am passing two params  uuid and type  along with file upload  Hope this will help who don t have the complex json data to send

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Since the only missing example is the ANDROID example  I ll add it  This technique uses a custom AsyncTask that should be declared inside your Activity class   private class UploadFile extends AsyncTask lt Void  Integer  String gt         Override     protected void onPreExecute                set a status bar or show a dialog to the user here         super onPreExecute                Override     protected void onProgressUpdate Integer    progress               progress 0  is the current status  e g  10              here you can update the user interface with the current status             Override     protected String doInBackground Void    params            return uploadFile               private String uploadFile              String responseString   null          HttpClient httpClient   new DefaultHttpClient            HttpPost httpPost   new HttpPost  http   example com upload-file             try               AndroidMultiPartEntity ampEntity   new AndroidMultiPartEntity                  new ProgressListener                          Override                         public void transferred long num                                   this trigger the progressUpdate event                             publishProgress  int    num    float  totalSize    100                                                           File myFile   new File   my image path example jpg                 ampEntity addPart  fileFieldName   new FileBody myFile                 totalSize   ampEntity getContentLength                httpPost setEntity ampEntity                   Making server call             HttpResponse httpResponse   httpClient execute httpPost               HttpEntity httpEntity   httpResponse getEntity                 int statusCode   httpResponse getStatusLine   getStatusCode                if  statusCode    200                    responseString   EntityUtils toString httpEntity                 else                   responseString    Error  http status                              statusCode                           catch  Exception e                responseString   e getMessage                      return responseString              Override     protected void onPostExecute String result               if you want update the user interface with upload result         super onPostExecute result              So  when you want to upload your file just call   new UploadFile   execute

[json] Posting a File and Associated Data to a RESTful WebService preferably as JSON

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